Image sensor including color and infrared pixels

Abstract

An image sensing system includes an IR notch filter configured to block transmission of spectral energy having wavelengths in an interface region between the visible and the invisible spectra and enable transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum, a digital image sensor including a two-dimensional array of pixel elements and configured to generate output signals at each pixel element as pixel data representing an image of a scene, and a color filter array including a two-dimensional array of selectively transmissive filters superimposed on and in registration with the two-dimensional array of pixel elements. The color filter array includes a first group of selectively transmissive filters disposed to transmit spectral energy in one or more colors of the visible spectrum and a second group of gray color filters disposed to transmit spectral energy in at least the near-infrared (IR) spectrum.

I claim: 
     
       1. An image sensing system, comprising:
 an IR notch filter configured to block transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum and enable transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum; 
 a digital image sensor comprising a two-dimensional array of pixel elements, the digital image sensor configured to generate output signals at each pixel element as pixel data representing an image of a scene; and 
 a color filter array comprising a two-dimensional array of selectively transmissive filters superimposed on and in registration with the two-dimensional array of pixel elements, the color filter array comprising a first group of selectively transmissive filters disposed to transmit spectral energy in one or more colors of the visible spectrum and a second group of gray color filters disposed to transmit spectral energy in at least the near-infrared (IR) spectrum, 
 wherein the IR notch filter is configured to block transmission of spectral energy having wavelengths between approximately 650 nm and approximately 780 nm, and 
 wherein the IR notch filter is configured to further block transmission of spectral energy having wavelengths above approximately 950 nm. 
 
     
     
       2. The image sensing system of  claim 1 , wherein the color filter array is formed by a repeating pattern of a pixel block, the pixel block comprising selectively transmissive filters disposed to transmit spectral energy in the red, green and blue colors of the visible spectrum and a gray color filter disposed to transmit spectral energy in the infrared spectrum. 
     
     
       3. The image sensing system of  claim 1 , wherein the gray color filter is formed using a linear combination of the red, green and blue color filters. 
     
     
       4. The image sensing system of  claim 3 , wherein the gray color filter is manufactured using the same material as the red, green and blue color filters. 
     
     
       5. The image sensing system of  claim 1 , wherein each of the pixel elements comprises a photodetector generating an output signal, and the image sensing system further comprises:
 a plurality of analog-to-digital conversion (ADC) circuits configured to convert the output signal from each pixel element to a digitized pixel voltage signal. 
 
     
     
       6. The image sensing system of  claim 5 , wherein the plurality of analog-to-digital conversion (ADC) circuits are located within the image sensor, each of the ADC circuits being connected to one or more photodetectors for converting the output signal of each pixel element to a digitized pixel voltage signal. 
     
     
       7. A digital imaging system, comprising:
 the image sensing system according to  claim 1 ; 
 a data memory in communication with the digital image sensor and configured to store the pixel data; and 
 a digital image processor in communication with the digital image sensor and the data memory and configured to process the pixel data to generate image data indicative of the image of the scene. 
 
     
     
       8. The digital imaging system of  claim 7 , wherein the digital image processor performs four-channel demosaicing to generate a first image using pixel data in the red, green blue colors and a second image using pixel data from the infrared spectrum. 
     
     
       9. An image sensing system, comprising:
 an IR notch filter configured to block transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum and enable transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum; 
 a digital image sensor comprising a two-dimensional array of pixel elements, the digital image sensor configured to generate output signals at each pixel element as pixel data representing an image of a scene; and 
 a color filter array comprising a two-dimensional array of selectively transmissive filters superimposed on and in registration with the two-dimensional array of pixel elements, the color filter array comprising a first group of selectively transmissive filters disposed to transmit spectral energy in one or more colors of the visible spectrum and a second group of gray color filters disposed to transmit spectral energy in at least the near-infrared (IR) spectrum, 
 wherein the gray color filter is formed using a linear combination of the red, green and blue color filters, and 
 wherein the gray color filter transmits spectral energy in the red, green and blue colors of the visible spectrum at 30% intensity and transmits spectral energy of the infrared spectrum at wavelengths above about 780 nm. 
 
     
     
       10. A digital imaging system, comprising:
 the image sensing system according to  claim 9 ; 
 a data memory in communication with the digital image sensor and configured to store the pixel data; and 
 a digital image processor in communication with the digital image sensor and the data memory and configured to process the pixel data to generate image data indicative of the image of the scene. 
 
     
     
       11. The digital imaging system of  claim 10 , wherein the digital image processor performs four-channel demosaicing to generate a first image using pixel data in the red, green blue colors and a second image using pixel data from the infrared spectrum. 
     
     
       12. The image sensing system of  claim 9 , wherein the color filter array is formed by a repeating pattern of a pixel block, the pixel block comprising selectively transmissive filters disposed to transmit spectral energy in the red, green and blue colors of the visible spectrum and a gray color filter disposed to transmit spectral energy in the infrared spectrum. 
     
     
       13. The image sensing system of  claim 9 , wherein the gray color filter is formed using a linear combination of the red, green and blue color filters. 
     
     
       14. The image sensing system of  claim 13 , wherein the gray color filter is manufactured using the same material as the red, green and blue color filters. 
     
     
       15. The image sensing system of  claim 9 , wherein each of the pixel elements comprises a photodetector generating an output signal, and the image sensing system further comprises:
 a plurality of analog-to-digital conversion (ADC) circuits configured to convert the output signal from each pixel element to a digitized pixel voltage signal. 
 
     
     
       16. The image sensing system of  claim 15 , wherein the plurality of analog-to-digital conversion (ADC) circuits are located within the image sensor, each of the ADC circuits being connected to one or more photodetectors for converting the output signal of each pixel element to a digitized pixel voltage signal. 
     
     
       17. A method for sensing an image of a scene comprising:
 receiving incident light at a digital image sensing system; 
 blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum; 
 blocking transmission of spectral energy having wavelengths between approximately 650 nm and approximately 780 nm; 
 sensing the incident light at a digital image sensor overlaid with a color filter array, comprising:
 sensing the incident light using a first group of selectively transmissive filters disposed to transmit spectral energy in one or more colors of the visible spectrum; and 
 sensing the incident light using a second group of gray color filters disposed to transmit spectral energy in at least the near-infrared (IR) spectrum; and 
 
 generating output signals at each pixel element of the digital image sensor as pixel data representing an image of a scene. 
 
     
     
       18. The method of  claim 17 , wherein blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum comprises:
 blocking transmission of spectral energy having wavelengths in an interface region between approximately 650 nm and approximately 780 nm. 
 
     
     
       19. The method of  claim 18 , wherein blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum further comprises blocking transmission of spectral energy having wavelengths above approximately 950 nm. 
     
     
       20. The method of  claim 17 , wherein sensing the incident light at a digital image sensor overlaid with a color filter array comprises:
 sensing the incident light using a color filter array formed by a repeating pattern of a pixel block, the pixel block comprising selectively transmissive filters disposed to transmit spectral energy in the red, green and blue colors of the visible spectrum and a gray color filter disposed to transmit spectral energy in the infrared spectrum. 
 
     
     
       21. A method for sensing an image of a scene comprising:
 receiving incident light at a digital image sensing system; 
 blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum; 
 sensing the incident light at a digital image sensor overlaid with a color filter array, comprising:
 sensing the incident light using a first group of selectively transmissive filters disposed to transmit spectral energy in one or more colors of the visible spectrum; and 
 sensing the incident light using a second group of gray color filters disposed to transmit spectral energy in at least the near-infrared (IR) spectrum, the gray color filters being disposed to transmit spectral energy in the red, green, and blue colors of the visible spectrum at 30% intensity and transmit spectral energy of the infrared spectrum at wavelengths above about 790 nm; and 
 
 generating output signals at each pixel element of the digital image sensor as pixel data representing an image of a scene. 
 
     
     
       22. The method of  claim 21 , wherein blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum comprises:
 blocking transmission of spectral energy having wavelengths in an interface region between approximately 650 nm and approximately 780 nm. 
 
     
     
       23. The method of  claim 22 , wherein blocking transmission of spectral energy having wavelengths in an interface region between the visible spectrum and the invisible spectrum while enabling transmission of spectral energy having wavelengths in at least the visible spectrum and the near-infrared (IR) spectrum further comprises blocking transmission of spectral energy having wavelengths above approximately 950 nm. 
     
     
       24. The method of  claim 21 , wherein sensing the incident light at a digital image sensor overlaid with a color filter array comprises:
 sensing the incident light using a color filter array formed by a repeating pattern of a pixel block, the pixel block comprising selectively transmissive filters disposed to transmit spectral energy in the red, green and blue colors of the visible spectrum and a gray color filter disposed to transmit spectral energy in the infrared spectrum. 
 
     
     
       25. The method of  claim 21 , further comprising:
 blocking transmission of spectral energy having wavelengths between approximately 650 nm and approximately 780 nm.